How does email open tracking work and what factors can affect its accuracy?

Email open tracking shows how many recipients opened your email, but its accuracy is affected by several technical factors. Understanding them helps you interpret campaign performance correctly.

How open tracking works

Pushwoosh embeds an invisible 1x1 tracking pixel in each email. When the recipient's client loads images, the pixel is downloaded from our server and recorded as an open (the PW_EmailOpen event).

What distorts the open rate

• Image blocking: if the client does not download external images by default, the pixel never loads and a genuine read is not counted. This under-reports opens.
• Apple Mail Privacy Protection (AMPP/MPP): Apple Mail on iOS, iPadOS and macOS pre-loads email content, including tracking pixels, through a proxy. This registers an open whether or not the person read the message, over-reporting opens. It applies to anyone using the Apple Mail app, regardless of their email domain - a Gmail address read in Apple Mail is affected too.
• Security scanners: corporate and ISP filters (for example Microsoft Defender for Office 365, Proofpoint or Mimecast) open emails and click links before the recipient does. Pushwoosh does not count these opens and clicks, so Opened and Clicked show what recipients did. Opens and clicks of older emails can still include scanners, so their rates can look higher than for recent emails.

Measuring around AMPP in Pushwoosh

You do not need to guess at the AMPP share - these features cover it directly:

• Human opens and Machine-only opens (AMPP) are shown in the Opened step of the email statistics for emails younger than 60 days. After 60 days the total still shows, but without this split.
• Excluded AMPP is shown alongside Opened unique. It is the open rate with AMPP-triggered opens removed. If it is close to the main rate, AMPP had little effect on that send. It is a comparison rate only - it does not change the Opened unique count.
• PW_EmailOpen.opened_by records who triggered the open: user for a genuine open, ampp for an Apple proxy pre-fetch. To build an audience of real openers, create a segment by event on PW_EmailOpen, click + Attribute and set opened_by to user.

Note that Hide My Email (addresses ending in @privaterelay.appleid.com) is a separate Apple feature. Counting those addresses tells you nothing reliable about MPP exposure - use Excluded AMPP and opened_by instead.

See Email statistics and default events for details.

Better engagement signals

• Clicks / Users clicked: a click is a deliberate action and a far cleaner engagement signal than an open.
• Custom events and conversions: track what users do after clicking - purchases, form submissions, in-app actions - to measure real campaign impact.